Insulated ball joint

ABSTRACT

System for loading and unloading of cold media, for example LNG or LPG, to or from a vessel, through pipes ( 1 ) connected with ball joints, where the pipes are insulated, and when each ball joint&#39;s inside part ( 4 ) has an inside pipe ( 3 ) which is sealed against the inside part ( 4 ) substantially over the letter extent, and which thereby forms an inside annulus ( 6 ) which can be evacuated, and that each ball joint&#39;s outside part ( 10 ) is surrounded by an outside annulus ( 9 ) which also may be evacuated.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a system for loading and unloading ofcold media, for example LNG or LPG, to or from a vessel, especiallyoffshore.

2. Description of the Prior Art

Today the loading and unloading of liquid natural gas or other cooleddown hydrocarbons take place offshore only as an exception. Wishes to dothis offshore are, however, increasingly natural. Floating factories forliquid natural gas, so called LNG, are being planned out on the openocean. Therefore the need for effective loading system is present.

Such a system is described in Norwegian patent application 1998 1332which contains descriptions of such loading systems. The loading systemitself consists of pipes connected with spherical ball joints. Inaddition what is described, the solution will be equipped with some typeof insulation. This is because the liquid LNG has a temperature of about−162° C. at atmospheric pressure.

This insulation has the task of minimize the loss of energy and thecosts in this connection. Further it is important to avoid cold surfaceswhere sea spray or moisture may form heavy layers of ice. Further taskis to avoid that ice is formed of ball joints smooth spherical surfaces.Such ice will be able to hinder the movement and damage the gasket andthereby make the system unusable.

Finally, the insulation should delay boiling if the loading is stoppedand pieces of pipe get under water.

Most types of insulation used on ship and in the offshore industries isbased on the fact that they contain a gas, usually air, which hinderboth heat conduction and heat radiation. But even if the heat radiationthrough the insulation is small, will heat conduction not be less thanthe heat conductivity of air.

It is estimated that, if this insulation shall meet the tasks as givenabove, there is a need for a 140 mm thick layer of insulation. This isproblematic, especially for the ball joint, where the insulation must bemounted inside.

The porous material must also be protected against a considerablemechanical wear and hits during various operations. This will furthermean problems with being able to dismount and inspect insulation andpiping as demanded by classification companies and others.

SUMMARY OF THE INVENTION

The present invention will avoid most of the above disadvantages withknown solutions, while it achieves other important advantages.

Accordingly, the present invention is a ball joint coupling apparatusfor loading and unloading of cold liquid gas media to or from a vesselthrough insulated pipes (1) connected with the ball joint couplingapparatus. The invention is characterized in that the ball jointcoupling apparatus has an inside part (4) which surrounds an inside pipe(3). The inside pipe (3) is sealed against the inside part (4)substantially over the extent of the inside part (4), thereby forming aninside annulus (6) which is evacuated.

The invention is also characterized in that the ball joint couplingapparatus has an outside part (10) which is surrounded by an outsideannulus (9) which is also evacuated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view, partly in section, of the ball joint of thepresent invention;

FIG. 2 is a longitudinal section view through a pipe insulated accordingto the present invention; and

FIG. 3 is a plan view, partly in section, of an alternate embodiment ofthe present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention consists of leading two hollow parts into oneanother, inside thin part 1 or 3 through which loading media can flow,and a somewhat thicker outside the part 2 or 4. The annulus is sealed inboth ends. In this way it is developed a flow passage 5 through thepipes and ball joints and an outside insulating annulus 11 through thepipes, and an outside insulating room 6 around the flow passage 5through the ball joint. The insulating annulus 6 and 11 are evacuatedthrough passage 7 when loading and unloading take place. Such a systemis easy to apply offshore.

The parts will be hollow, that they are all having an insideflow-through passage 5 or a surrounding annulus 6 or 11. Theconstruction may be for example as shown with the ball joints on FIG. 1and the pipe on FIG. 2. The pipe may typically have a length of 8meters. Typical inside diameter for ball join may be 200 till 600 mm.The shaping of the ball joint will be such that the heat flow from theball joint's inside part 4 to the loading medium will be low. This willeliminate the problems with ice forming and damage on gaskets becausethe ball surface is warmer than 0° C.

At loading it may be a great temperature differences between outside andinside parts. The thermal tension for straight pipes are drasticallyreduced by the fact that there is a built in section 8 in the loadingpipe which is flexible in axial direction. This will have an adequateforming and dimensioning to be able to withstand actual loading andexhausting strains.

The air space between the pipes has an insulating effect. But theinsulating ability will be better than other methods only when the airin between is sucked out through a valve. The insulating ability willthen be independent of the thickness of the air space. This willsubstantially limit the ball joints dimensions.

The heat conduction will stop simply because there are no molecules thattransport the heat. Heat radiation is also modest at low temperature,and is dependent on the surfaces, so that these should be treated with alacquer or other material gives a low emissivity.

Insulation method is not a part of the invention. It was invented by SirJames Dewer in the last century, add is being used for example inthermos bottles and for storing of liquid air in so-calledDewar-containers. The inventor does not know that the method is beingapplied on ball joints, pipe parts or such loading systems as describedhere.

With the insulated pipes and ball joints according to the presentinvention, one achieve very slight energy losses at loading, without anyrisk for intense boiling if the loading stops, and there are plusdegrees on the outside of both the pipes and the ball joints, and thereare no problems with ice forming.

Further according to the invention, there is also achieved a separationof the elements that receive impacts and take up outside forces, fromthe pipe that transfer the “dangerous” medium. This is the most correctwith respect to the risk for brake and leakages.

Insulated pipes and ball joints according to the invention also make itpossible a quick cooling down of the pipe system without greattemperature stresses in the piping walls. Low building costs, longlimetime and simple inspection of all parts are other importantadvantages with the invention.

If gas should leak into the strength pipe and the insulating ability isreduced, will this be visible by the formings of frost on the outside.This provides a system with an extra security.

As shown on FIG. 3, a ball joint may include both an inside annulus 6inside the ball joint's inner part 4 and an outside annulus 9 outsidethe ball joint's outer part 10, since both the outside and the insideannulus is adapted to be evacuated, in order to achieve an optimalinsulation of the ball joints against the surroundings.

What is claimed is:
 1. A ball joint coupling apparatus for loading andunloading of cold liquid gas media to or from a vessel through pipes (1)connected with said ball joint coupling apparatus, where the pipes areinsulated, characterized in that said ball joint coupling apparatus hasan inside pipe (3) and an inside part (4), said inside part (4)surrounding said inside pipe (3), said inside pipe (3) being sealedagainst the inside part (4) substantially over the extent of the insidepart (4), thereby forming an inside annulus (6), said inside annulus (6)being evacuated, and in that said ball joint coupling apparatus has anoutside part (10), said outside part (10) being surrounded by an outsideannulus (9), said outside annulus (9) also being evacuated.
 2. A balljoint coupling apparatus as claimed in claim 1, characterized in thatsaid inside part (4) is effectively insulated against said cold liquidgas media such that the temperatures of said inside and outside parts(4,10) may be different from the temperature of said cold liquid gasmedia.